Alternate substrate inhibitors and dead-end inhibitors of phenylethanolamine N-methyltransferase (PNMT) have been designed and are being synthesized to probe the requirements of the binding site of PNMT and allow more potent and more specific inhibitors of this enzyme to be prepared and evaluated. The effects of in vivo inhibition of PNMT are of interest, e.g., potential role of PNMT and epinephrine in blood pressure regulation.